A comeback. Usually the last resort in an argument, but sometimes the first if you can't be bothered with an argument or conversation. Normally short for "I had your maw" (meaning "I had sexual intercourse with your mother")
'That's shite.'
'So's yer maw.'
'You owe me.'
'Yeah, well your maw owes me for last night.'
'You're such a gay.'
'I think your maw would disagree.'
'Fuck you.'
'Shit, watch out. Here comes your maw, an' it looks like she's got an erection.'